Certain kinds of patients require periodic injections of fluid medicine into their bodies. An example of one kind of patient is a cancer patient who needs to have injected into his body exact amounts of medicine at periodic periods of time.
One way to accomplish this is to hospitalize the patient for the time necessary to inject the medicine at periodic times by hospital personnel. This ties up needed hospital space and personnel because in many such cases, the patient can be ambulatory, but in order to obtain proper medication, he must be hospitaized. The administering of such medication by hospital personnel can result in inaccurate doses and at inprecise times.
Another way to medicate such a patient is to utilize a known portable infusion device as disclosed in U.S. Pat. No. 3,384,080 which constantly injects therapeutic fluids into a human body by means of a pump that is powered by a spring motor, the speed of which is controlled by a watch escapement unit. This device is not satisfactory because it constantly feeds medicine into the body, the spring motor has to be manually rewound, the pump uses rollers that roll along the tubing which causes creep and stretching of the tubing thereby causing inaccurate amounts of medicine to be injected into the body and it creates momentary backflow pressure conditions which can have harmful effects.